1. Field of the Invention
The present invention relates to averaging axial and/or axial-diametral extensometers.
2. Description of the Prior Art
In the prior art, so-called "bi-axial" strain measurement extensometers have been known. For example, U.S. Pat. No. 4,251,918 shows a type of bi-axial extensometer which is used for measuring axial and/or diametral strains in material test specimens. The device shown in that patent includes four extensometer arms, two on each side of the specimen. The arms on opposite sides of the specimen are connected by a flat spring member and are oriented to have upper and lower arms that are opposite from each other. The arms are constructed to provide means for measuring axial strain and also for measuring diametral changes of the specimen. The diametral measurement is biased toward sensing the diametral changes between the specimen engaging points of the lower arms.
U.S. Pat. No. 3,789,508 illustrates an extensometer which has a cross flexure support between the arms. The individual extensometer sections of the present invention also use such mounting for the arms of the sections for measuring axial strain. The cross flexure mounting permits relative movement between the outer ends of the arms in direction along the axis of the specimen, but restrains movements in other axes.
Reference is made to copending application Ser. No. 474,700, filed Mar. 11, 1983 now U.S. Pat. No. 4,491,021 for An Axial-Torsional Extensometer, which illustrates extensometer sections mounted on opposite sides of a specimen, and diametrically opposed, but resupported to have different degrees of freedom to measure torsional strains, as opposed to diametral strains and also measuring average axial changes as in the present device.